A method is described for the label-free detection of DNA hybridization on porous silicon (por-Si), based upon the pairing of oligonucleotide chemistry and standard silicon nanotechnology. Por-Si with a pore diameter of approximately 30 nm was used to immobilize probe DNA. Infrared microspectroscopy was employed to monitor the hybridization of probe-DNA immobilized on pore surfaces with its complementary DNA (target-DNA). The immobilization of probe DNA on por-Si facilitates hybridization detection for a small sensing area (approximately 50×50 μ m2) with a high detection efficiency. In this study, we fabricated a porous silicon-based DNA microarray (por-Si-microarray) using photolithographic and Si anodizing techniques. We demonstrate that DNA hybridization can be detected on a por-Si-microarray through the analysis of infrared absorption spectral profiles in the region where the vibration modes of the bases appear. This present approach demonstrates that por-Si-microarray in conjugation with infrared microspectroscopy has potential application in DNA sensing chips.